4,971 research outputs found

    High-throughput enzyme evolution in Saccharomyces cerevisiae using a synthetic RNA switch

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    Metabolic engineering can produce a wide range of bulk and fine chemicals using renewable resources. These approaches frequently require high levels of activity from multiple heterologous enzymes. Directed evolution techniques have been used to improve the activity of a wide range of enzymes but can be difficult to apply when the enzyme is used in whole cells. To address this limitation, we developed generalizable in vivo biosensors using engineered RNA switches to link metabolite concentrations and GFP expression levels in living cells. Using such a sensor, we quantitatively screened large enzyme libraries in high throughput based on fluorescence, either in clonal cultures or in single cells by fluorescence activated cell sorting (FACS). By iteratively screening libraries of a caffeine demethylase, we identified beneficial mutations that ultimately increased the enzyme activity in vivo by 33 fold and the product selectivity by 22 fold. As aptamer selection strategies allow RNA switches to be readily adapted to recognize new small molecules, these RNA-based screening techniques are applicable to a broad range of enzymes and metabolic pathways

    Revolutionary Coalition Strength and Collective Failure as Determinants of Status Reallocation

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    This experiment investigated the effects of collective performance and coalition strength on the redistribution of status prerogatives in triads. A status hierarchy was established within triads, such that one person held higher control status and the two others held lower status. Each group performed an ambiguous, decision-making task over two trials. Collective performance (i.e., success vs failure) was manipulated via bogus feedback regarding the group’s performance, while coalition strength was manipulated by varying the extent to which the two low-status members, acting together as a revolutionary coalition, could damage the outcomes received by the high-status member. Results indicate a collective-performance main effect, with the control prerogatives of the high-status person being reduced more under failure than under success. This effect is mediated by member dissatisfaction with the group’s activities. As predicted, the results also indicate a significant Collective Performance X Coalition Strength interaction effect. Strong coalitions achieved more extensive reallocation of status prerogatives than weak ones, but this occurred only on the second trial for groups experiencing recurring failure. This effect elucidates some of the difficulties involved in mobilizing joint efforts to exercise coalition-based influence

    Callosphecodes, a little-known bee (Hymenoptera, Halictidae, Sphecodes)

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    Callosphecodes Friese, 1909, a synonym or perhaps subgenus of Sphecodes Latreille, 1804, is known on the basis of one female of Sphecodes ralunensis (Friese, 1909)from New Britain and one female and one male of a similar species, Sphecodes manskii (Rayment, 1935) from northeastern Australia. The male is here described for the first time and the females of the two species are compared for the first time. In spite of considerable collecting, only these three specimens have appeared in over a century. Descriptions and illustrations are provided

    Perceptions of risk and social disorder can have a huge impact on local political engagement

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    The ‘broken windows’ theory has dominated policy debates over how to deal with crime and disorder for more than three decades, but few have examined how disorder influences political engagement. Using data from Chicago, Jamila Michener finds that people’s perceptions of disorder are a powerful influence on their likelihood to engage politically, such as speaking to a politician or attending a community meeting. She argues that the way people interpret the ‘broken windows’ of their neighborhoods can be a critical determinant of how grassroots politics develop

    Health Inspections of Private Homes - Frank v. Maryland

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    The presence of more parties in a governing cabinet can encourage greater transparency

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    Secrecy is often assumed to be a guiding value of governments, with parties in office tending not to prefer opening up the fullness of their record to public scrutiny, with single-party governments particularly seen as likely to follow this secretive path. Gregory Michener argues that this impulse can be tempered by the presence of more parties in the Cabinet, which create incentives towards greater transparency

    The Strongest Thing in the World

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    Pages 91-10
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